In the planting of genetically changed crops around the world, the U.S. government has done just about everything it can to help except drive the tractor.

Agriculture Secretary Dan Glickman has been one of biotechnology's leading boosters, admonishing reluctant Europeans not to stand in the way of progress and urging the acceptance of food grown using the new, American technology.But lately, Glickman has turned cautious. In St. Louis recently, he warned that the United States must pay closer attention to questions being raised around the world about genetic engineering. ''We can't force-feed . . . reluctant consumers,'' he said.

His words, along with a recent scientific finding that biotechnology may harm butterflies, are helping trigger an emerging debate in this country that could prove pivotal for the new technology and for its driving force, St. Louis-based Monsanto Co.

In an interview in Washington not long ago, Glickman said biotechnology ''shouldn't be a steamroller . . . . Ultimately, if the consumer doesn't buy, the technology isn't worth a damn. Period.''

He said European concerns about the potential health and environmental effects of modified crops are taking a toll on U.S. grain exports.

''There are certainly more and more questions being asked about biotechnology, and those questions must be answered,'' Glickman said. ''They cannot be brushed off. They must be dealt with.''

After years of muted concerns about biotechnology in the United States, Washington is suddenly brimming with new studies and discussions:

* A White House task force will report as early as July on the prospect of labeling genetically engineered foods, the administration disclosed.

* The National Academy of Sciences is planning a biotechnology review that will focus on seeds and ownership of genetic materials.

* Glickman is resurrecting a biotechnology advisory committee that will have a wide array of experts, members of the public and critics.

If that weren't enough new activity, wealthy foundations are considering plowing millions of dollars into a public awareness campaign that would be conducted by environmental advocacy groups.

''There is a shift. It might even be a sea change,'' Margaret Mellon of the Union of Concerned Scientists said of the new attention in the United States to genetic engineering.

Jay Byrne, a Monsanto spokesman, said he regards the attention as positive. Three government studies published this month in Europe - by the Irish Food Authority, by a British House of Commons committee and by a British Ministry of Agriculture panel - found no human health implications from gene-altered food. As Byrne sees it, the flurry of new studies in Washington can allay any fears that might be sprouting.

The emerging debates will include topics as large as corporate mergers in agriculture - which Glickman also is warning about - and as small as the butterfly.

In a report that accelerated the biotech debate globally, Cornell University scientists said monarch butterflies could be threatened by certain modified crops. They found that nearly half of the caterpillars in laboratory tests died after eating the pollen of corn engineered with Bt (bacillus thuringiensis) bacteria to resist pests.

The monarch study gave people a touchstone in a complex matter that most Americans haven't thought a lot about.

For European leaders, it was evidence to raise more barriers to the technology. The 15-nation European Union said it would suspend further consideration of approvals for modified corn. Austria banned cultivation of Monsanto's engineered corn, and a French official said his country might revisit its past approval of a Monsanto hybrid.

Besides encouraging public debate, Glickman is raising eyebrows among insiders who watch the politics of genetic engineering. His public shift from cheerleader to probing realist began a month ago in a speech at Purdue University. ''When it's all said and done, the public opinion poll is just as powerful a research tool as the test tube,'' Glickman said in the speech.

In an interview, Glickman said he was trying to send a message not just to the American people but to others in government. He said he remains committed to biotechnology as important both to human health and to farming. But, he added, a better job has to be done about building confidence.

Glickman surprised participants on all sides of the debate, among them Charles Benbrook, a consultant who has worked for Congress and the National Academy of Sciences since the early 1980s. When word of Glickman's all-but-ignored speech at Purdue filtered out, Benbrook said, ''People's jaws dropped. . . . It was probably the most dramatic turnaround in the message of a secretary of agriculture that I've seen.''

Unlike their European counterparts, most pro- environment organizations in the United States have paid scant attention to genetic engineering. Some American groups may have been persuaded by the potential of modified crops to reduce the spraying of farm chemicals.

Some groups had their plates full, while others lacked resources to pursue a complicated issue that requires scientific expertise. This lack of attention has befuddled their European counterparts but may change soon with an infusion of money from foundations.

The Chicago-based Joyce Foundation is among several foundations that have been gathering information on genetic engineering for a meeting to be held next month in New York. Participants have put together an inch-thick workbook on biotechnology that they will distribute to representatives of foundations that fuel much of the work of America's environmental advocacy groups.

Monsanto's Byrne said that Monsanto is happy to participate in any new talks. ''All too often, this debate can be polarized by the extremes of fear or concern and those of hope,'' he said. ''The best public service is to have an informed debate in the middle,'' he said.

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